The majority of conventionally mass-produced piezoelectric ceramic compositions are PZT (lead zirconate titanate) materials and thus contain lead. In recent years, the development of lead-free piezoelectric ceramic materials has been desired in order to eliminate the adverse influence of lead on the environment. As such lead-free piezoelectric ceramic materials (called “lead-free piezoelectric ceramic compositions”, there have been proposed those represented by the compositional formula: ANbO3 (where A is an alkali metal) such as potassium sodium niobate ((K,Na)NbO3). However, the lead-free ANbO3 piezoelectric ceramic compositions themselves have the problem of poor sinterability and moisture resistance.
As a measure against this problem, Patent Document 1 discloses a technique of adding Cu, Li, Ta or the like to a lead-free ANbO3 piezoelectric ceramic composition so as to obtain improvements in sinterability and in piezoelectric properties.
Further, Patent Document 2 discloses a lead-free piezoelectric ceramic composition represented by the general formula: {Lix(K1−yNay)1−x}(Nb1−zSbz)O3 (where 0≦x≦0.2; 0≦y≦1.0; and 0≦z≦0.2 except for the case of x=z=0) and capable of showing relatively good sinterability and piezoelectric properties.